This week Jonathan and Aaron chat with Piers Finlayson about One ROM! Why does the retro-computing world need a solution for replacement ROMs? How difficult was it to squeeze a MCU and layout into the original ROM footprint? And what’s next for the project? Listen to find out!
Continue reading “FLOSS Weekly Episode 850: One ROM To Rule Them All”
The familiar five volts standard from back in the TTL days always struck me as odd. Back when I was just a poor kid trying to cobble together my first circuits from the Forrest Mims Engineer’s Notebook, TTL was always a problem. That narrow 4.75 V to 5.25 V spec for Vcc was hard to hit, thanks to being too poor to buy or build a dedicated 5 V power supply. Yes, I could have wired up four 1.5 V dry cells and used a series diode to drop it down into range, but that was awkward and went through batteries pretty fast once you got past more than a few chips.
As a hobbyist, the five volt TTL standard always seemed a little capricious, but I strongly suspected there had to be a solid reason behind it. To get some insights into the engineering rationale, I did what anyone living in the future would do: I asked ChatGPT. My question was simple: “How did five volts become the standard voltage for TTL logic chips?” And while overall the answers were plausible, like every other time I use the chatbot, they left me wanting more.
Taking on a refrigerator-sized minicomputer is not for the faint-hearted, but [Usagi Electric] has done it with a DEC PDP-11/44. He’s not doing it in half measures either, for his machine is tricked out with an impressive array of upgrades. Among them however is no storage, and with two co-processors there’s a meager 3U of rack space left. The plan is to fit a period 8″ hard drive in the space alongside a TU50 tape dive, and it’s this final component that’s the subject of his latest video.
DEC never did anything by halves, and a DECTape II cartridge is more than a simple container for tape reels. Instead it has a capstan of its own that engages with one in the drive, and an internal drive belt that moves the reels. All the rubber parts in both tapes and drive are thoroughly perished, and it’s impressive that he manages to find inexpensive modern polymer alternatives. The original drive is probably intended for a VAX system, thus it has the interesting feature of a second drive mechanism out of sight to hold a tape containing microcode.
Having reconditioned the drive, it goes in behind a custom front panel, and though there’s no useful data to test it with on the tapes he has, it appears all working. You can see it all in the video below the break, and if you’re interested further we’ve covered this machine in the past.
Continue reading “A Minicomputer Tape Drive Receives Some Love”
Glasses are perhaps the most non-invasive method of vision correction, followed by contact lenses. Each have their drawbacks though, and some seek more permanent solutions in the form of laser eye surgeries like LASIK, aiming to reshape their corneas for better visual clarity. However, these methods often involve cutting into the eye itself, and it hardly gets any more invasive than that.
A new surgical method could have benefits in this regard, allowing correction in a single procedure that requires no lasers and no surgical cutting of the eye itself. The idea is to use electricity to help reshape the eye back towards greater optical performance.
Continue reading “Reshaping Eyeballs With Electricity, No Lasers Or Cutting Required”
Over on brushless.zone, we’ve come across an interesting write-up that details the construction of a dam control system. This is actually the second part, in the first, we learn that some friends purchased an old dysfunctional 80 kW dam with the intention of restoring it. One friend was in charge of the business paperwork, one friend the mechanical side of things, and the other was responsible for the electronics — you can probably guess which ones we’re interested in.
The site controller is built around a Nucleo-H753 featuring the STM32H753ZI microcontroller, which was selected due to it being the largest single-core version of the dev board available. This site controller board features a dozen output light switches, sixteen front-panel button inputs, dual 24 V PSU inputs, multiple non-isolated analog inputs, atmospheric pressure and temperature sensors, multiple analog multiplexers, a pair of SSD1309 OLED screens, and an ESP32 for internet connectivity. There’s also fiber optic TX and RX for talking to the valve controller, a trio of isolated hall-effect current sensors for measuring the generator phase current, through current transformers, four contactor outputs (a contactor is a high-current relay), a line voltage ADC, and the cherry on top — an electronic buzzer.
The valve controller has: 48 V input from either the PSU or battery, motor phase output, motor field drive output, 8 kV rated isolation relay, limit switch input, the other side of the optical fiber TX and RX for talking to the site controller board, and connectors for various purposes.
If you’re interested in seeing this dam control system being tested, checkout the video embedded below.
Continue reading “Homebrew Dam Control System Includes All The Bells And Whistles”
There’s something extremely calming and pleasing about watching a screensaver that merely bounces some kind of image around, with the DVD logo screensaver of a DVD player being a good example. The logical conclusion is thus that it would be great to replicate this screensaver in Lego, because it’d be fun and easy. That’s where [Grant Davis]’s life got flipped upside-down, as this turned out to be anything but an easy task in his chosen medium.
Things got off on a rocky start with figuring out how to make the logo bounce against the side of the ‘screen’, instead of having it merely approach before backing off. The right approach here seemed to be Lego treads as used on e.g. excavators, which give the motion that nice pause before ‘bouncing’ back in the other direction.
With that seemingly solved, most of the effort went into assembling a functional yet sturdy frame, all driven by a single Lego Technic electromotor. Along the way there were many cases of rapid self-disassembly, ultimately leading to a complete redesign using worm gears, thus requiring running the gears both ways with help from a gearbox.
Since the screensaver is supposed to run unattended, many end-stop and toggle mechanisms were tried and discarded before settling on the design that would be used for the full-sized build. Naturally, scaling up always goes smoothly, so everything got redesigned and beefed up once again, with more motors added and multiple gearbox design changes attempted after some unfortunate shredded gears.
Ultimately [Grant] got what he set out to do: the DVD logo bouncing around on a Lego ‘TV’ in a very realistic fashion, set to the noise of Lego Technic gears and motors whirring away in the background.
Thanks to [Carl Foxmarten] for the tip.
Continue reading “Building The DVD Logo Screensaver With LEGO”
Nature is known for its intense beauty from its patterns and bright colors; however, this requires going outside. Who has time for that insanity!?!? [Bleuje] provides the perfect solution with his mesmerizing display of particle behavior.
